This invention relates to a stackable cassette for supporting a plurality of sample containers, such as test tubes, having different diameters and/or lengths and transporting them to a testing or sample aspiration station. More particularly, the invention concerns the transportation and identification of sealed test tubes having different diameters and lengths in a hematology analyzer of the type which heretofore required the manual introduction of a blood sample held in vertically oriented, open-mouthed containers of the same size. Full automation is accomplished by being able to utilize, in the same cassette, test tubes of varying sizes containing blood samples. Such a cassette obviates the requirement of first having to manually remove and transfer the blood samples in those containers which are not adapted to be received properly in the receptacle/s of a cassette which is only designed to properly receive test tubes of one size. It also obviates the requirement of providing a plurality of different cassettes each of which is capable of properly receiving test tubes of one of the differing sizes of test tubes expected to be received in a hematology laboratory together with a hematology analyzer which is compatible with such plurality of different cassettes. Such full automation is practical only in an optimized system which utilizes the same cassettes to receive blood samples in tubes of serveral different diameters and/or lengths and which is fully capable of sequentially receiving them even though randomly placed in the cassette, it being a given that it is common practice to collect blood samples in tubes having several different lengths and/or diameters.
Automatically operated transporter apparatus for sequentially performing aspirating functions on a plurality of substantially vertically oriented, open-mouthed test tubes containing blood samples which tubes are arranged in staggered positions in two columns in a common rack and which tubes are alternately titled under an aspirating tip is taught in U.S. Pat. No. 3,768,526, Automatic Test Tube Transporter and Sample Dispenser, issued Oct. 30, 1973, to Sanz et al. Sanz et al states:
"Referring now to FIG. 5 there is shown a cross-section of the rack 200. The test tubes 207' are shown received in the racks and are normally biased upright by a spring 222 held against the back wall 205. Spring 222 maintains resilient pressure on tube 207'. As post 124 passes through slots 215 and encounters the walls of the test tubes, it pushes them and they tilt into the position shown in FIG. 5. PA1 When a smaller test tube is used it is desirious to have the tip hit the inner wall thereof at approximately the same point. In these cases an adaptor block 220 is used (FIG. 6). The block is shaped similar to test tube 207 so that it will tilt in the same manner. The smaller tube is received in a bore 221 of smaller diameter than adaptor 220. Adaptor 220 also has a projection 224 which is adapted to fit into notch 207. This is to insure that the smaller test tube is in proper orientation for the tip 618 to be received therein. PA1 It should be noted that the taper 208 of hole 206 and the elliptical shape and taper 210 of holes 209 accommodate the tilting of test tube 207'. PA1 In the embodiments of the rack shown in FIGS. 5 and 6 the member 204' has recessed areas 212' which act in the same manner as slots 212." (column 4, line 44 to column 6, line 6).
Part of the wiper and tip mechanism 600 is shown in FIG. 5 and the device is so arranged that the tip 618 hits the inner wall of test tube 207' at point X. This is important since if the aspiration and dispensing do not take place along this inner side splashing occurs which is not desired due to loss of liquid, agitation and bubble formation.
This apparatus' loading and transporting procedure and mode, respectively, suffer from the obvious drawbacks inherent in having the sample test tubes open to atmosphere at all times, as well as requiring additional manual handling to place smaller test tubes in adaptor blocks having the proper sized receptacle therein, and the further requirement that sealed test tubes have their sealing stoppers manually removed prior to usage therein. The later requirement presents additional problems, since the opening of the whole blood container, which typically is under a small vacuum by virtue of the blood collecting technique, permits an aerosol to escape into the laboratory close to the technician who is operating the system. Such aerosol can contain blood related impurities and transmit disease, such as hepatitis. Furthermore, the apparatus and its racks do not provide for sample mixing nor are the racks themselves suitable for mixing particularly as their containers are open-mouthed and designed to be tilted within the stationary rack. Additionally, the two column staggered, substantially vertical, positional design requirement of the rack and the apparatus' requirement of open-mouthed containers are inherent limitations which do not easily lend themselves to utilization in a fully automated hematology analyzer of the type that this cassette's inventive design permits.